Apparatus and methods for liquid sample handling based on capillary action

The present invention comprises a removable capillary tip insert which provides for replacement of an individual capillary in the dispensing head of an automated liquid handling apparatus. In some embodiments, the insert has been designed to accept variable capillary lengths while maintaining a constant length protruding from the insert. In a preferred embodiment, the removable capillary insert of the invention comprises a head adapted to accept an insertion tool and tapered to seat in the dispense head; a shaft with external threads which form a threaded collar that permits the insert to be screwed into the dispense head; a lumen running internally from the proximal to the distal ends of the head and shaft which forms a hollow interior in the insert in which a capillary resides; and a capillary tube of user-selected liquid capacity. One embodiment, without limitation, comprises a molded plastic part with an integral capillary tube. Other embodiments comprise dispensing heads with various configurations of capillary inserts and methods for automated liquid dispensing using the same.